(1) Field of the Invention
The present invention relates generally to a method of impregnating porous abrasive media with a liquid and, more particularly, to a method for impregnating porous abrasive media with a reactive solution for use in distressing fabric and the product produced thereby.
(2) Description of the Prior Art
"Stone washing" generally consists of exposing the garments, such as denim jeans, to a porous abrasive media which has been impregnated with a reactive solution such as an aqueous solution of either potassium or sodium permanganate or sodium hypochlorite. The treatment process achieves a softening as well as a pre-faded condition which is desirable.
One of the problems with stone washing relates to the difficulty of getting the reactive solution to completely impregnate the porous abrasive media. The porous abrasive media is generally lighter than the reactive solution and thus floats on the solution. The media has previously been placed in buckets and forced down in the solution so that the solution impregnates the rock. However, because this process was carried on ambient pressure, some air was trapped in the porous abrasive media and prevented the reactive solution from completely penetrating the media.
As a result, it has become common practice to employ vacuum to assist in impregnating the porous abrasive media for stone washing. Two examples of this process are shown in U.S. Pat. Nos. 4,816,033, issued to Hoffer et al., and 4,850,156, issued to Bellaire. The entire disclosure of these patents are hereby incorporated by reference.
The Hoffer patent discloses a technique by which pumice rock is impregnated with potassium permanganate solution by placing the rock in a sealed chamber, drawing a vacuum in the chamber, spraying a potassium permanganate solution in to the chamber while the vacuum drops to a preselected level, and then retrieving the impregnated rock from the chamber.
The Bellaire patent discloses a method of preparing porous abrasive rock for use in distressing fabric by the steps of impregnating the rocks placed in a vacuum vessel with a bleaching solution under reduced pressure, maintaining the reduced pressure for a first interval while injecting the solution beneath the rocks and then increasing the vessel pressure to approximately ambient prior to removal.
While the techniques taught by Hoffer and Bellaire are useful, there are some limitations. Specifically, the time required to impregnate the porous abrasive media is generally about 15-25 minutes. Since this is a batch-type process, the time required limits the amount of media which can be impregnated. In addition, it has been surprisingly discovered that repeated vacuum cycles result in a higher impregnation level in less time than the techniques taught by either Hoffer or Bellaire. This higher impregnation level results in superior stone washing results.
Thus, there remains a need for a new and improved method for impregnating porous abrasive media with reactive solution which requires less time to impregnate the rock and, in addition, results in a higher degree of impregnation.